1. Field of the Invention
The present invention relates to a composition which stably comprises urea and which is intended, in particular, for use in the fields of cosmetics and/or dermatology. The invention also relates to a use of this composition for the care, the treatment, the protection and/or hydration of human skin, of mucous membranes and/or keratin fibers, and for the treatment of dry skin.
2. Discussion of the Background
In cosmetic or dermatological compositions, moisturizers, i.e., hygroscopic substances which allow the water content in the skin to be retained and thus the suppleness and the touch of the skin to be affected advantageously, are widely used. Such moisturizers are also useful for hydrating the skin and, in particular for treating dry skin.
Among the many moisturizers, urea is particularly important. Urea is a component of the NMF (natural moisturizer factor) and has a softening effect on the corneal layers of the skin.
However, the disadvantage of urea is that it is generally not stable in an aqueous environment, where it degrades into carbon dioxide and ammonia. This leads to a rise in pH of the composition containing it and the release of an odor, which make the use of such compositions very unsatisfactory.
It has therefore been attempted for a long time to formulate urea in cosmetically acceptable compositions in a form which is stable over at least several months. Thus, document JP51048441 describes the stabilization of urea in a glycine/sodium hydroxide buffer at a pH of 6 to 9. However, the use of such a buffer has the disadvantage of making the composition containing it sticky when applied to the skin.
Accordingly, there remains therefore the need for stable urea-based compositions which have satisfactory cosmetic properties.